We have no trio packaged yet.
https://github.com/python-trio/trio/issues/1437

--- anyio-4.12.1/src/anyio/_core/_eventloop.py.orig
+++ anyio-4.12.1/src/anyio/_core/_eventloop.py
@@ -26,7 +26,7 @@
     from ..abc import AsyncBackend
 
 # This must be updated when new backends are introduced
-BACKENDS = "asyncio", "trio"
+BACKENDS = "asyncio",
 
 T_Retval = TypeVar("T_Retval")
 PosArgsT = TypeVarTuple("PosArgsT")
--- anyio-4.12.1/pyproject.toml.orig
+++ anyio-4.12.1/pyproject.toml
@@ -153,7 +153,6 @@
 package = "editable"
 commands = [["coverage", "run", "-m", "pytest", { replace = "posargs", extend = true }]]
 dependency_groups = ["test"]
-extras = ["trio"]
 set_env = { PYTEST_DISABLE_PLUGIN_AUTOLOAD = "1" }
 
 [tool.tox.env.pypy3]
--- anyio-4.12.1/tests/test_taskgroups.py.orig
+++ anyio-4.12.1/tests/test_taskgroups.py
@@ -72,7 +72,6 @@
     "modulename",
     [
         pytest.param("asyncio"),
-        pytest.param("trio"),
     ],
 )
 def test_run_natively(modulename: str) -> None: